The present invention relates in general to a printing cylinder and in particular to a gapless print cylinder assembly having an integral compressible layer.
A typical cylinder on an offset printing press includes an axially extending groove, or lock up gutter with clamping segments. Printing blankets are provided in sheets that are wrapped around the cylinder such that the opposite ends of the printing blanket are inserted and clamped in the groove. Because the loose ends of the blanket must be secured to the cylinder, the surface of the blanket when mounted will have a gap where the edges are drawn. As a consequence, print quality, speed of operation and available print region dimensions are affected. Also, press downtime due to printing blanket change over time can be excessive.
Press downtime associated with printing blanket change over can sometimes be minimized where the printing blanket is provided as a gapless printing sleeve that is capable of mounting onto the cylinder. The printing sleeve typically includes several layers including a base sleeve, a compressible layer, and a printing face. During use, the printing sleeve is stretched over the cylinder and is thus exposed to considerable peripheral and circumferential forces. Additionally, while operating the press, the printing sleeve is exposed to high revolution speeds and the printing face of the sleeve is exposed to impact with other components of the press, including printing plates of a plate cylinder. As such, the printing sleeve will eventually dynamically fatigue. Where the printing sleeve has experienced sufficient dynamic fatigue, print quality will be affected, requiring replacement. However, it is usually either the printing surface, or the adhesive that holds the printing surface to the internal layers, that will fail. The remaining layers are often functionally and structurally intact.
Currently, some fatigued printing sleeves are discarded. This leads to considerable waste and cost as the materials used to construct the base layer and internal layers, including the compressible layer, constitute a significant portion of the total materials cost for the sleeve production. Alternatively, the fatigued printing sleeves may be sent back to the manufacturer to be reconditioned or xe2x80x9crecappedxe2x80x9d. While reconditioning allows for recycling of certain reusable portions of the fatigued printing sleeve, the press operator must ship the entire printing sleeve back to the manufacturer. The manufacturer must remove the worn portions of the printing sleeve, and assemble a new printing surface and internal components to the printing sleeve. This causes considerable cost to the manufacturer. Further, in the course of shipping a printing sleeve, it is possible to damage the otherwise in tact layers causing increased cost and delay.
The present invention overcomes the disadvantages of previous printing sleeves and cylinders by providing a gapless cylinder assembly having an integral compressible layer. The cylinder assembly is arranged to receive replaceable printing surfaces.
According to one embodiment of the present invention, a gapless print cylinder assembly includes an inner shell having a first end portion, a second end portion, and a body portion. A support carrier is coupled to the inner shell about each of the first and second end portions. The support carrier is adapted to support the gapless print cylinder assembly when mounted on a press. For example, the support carrier may include first and second plugs that define spaced end journal and bearing members. An outer shell is positioned over and generally coaxial with the inner shell, and a compressible layer is located between the inner shell and the outer shell. A printing sleeve is attached, but removable from the outer shell of the cylinder assembly such that when the printing sleeve is mounted on the cylinder assembly, lateral and rotational motion of the printing sleeve with respect to the cylinder assembly is prevented.